This invention relates generally to slit valve assemblies and methods and more particularly to slit valve assemblies and methods used in semiconductor manufacturing equipment.
Semiconductor manufacturing equipment often include a number of adjacent but independently sealable chambers. For example, a single piece of semiconductor manufacturing equipment might include a number of processing chambers and one or more load-lock chambers clustered around a central robotic transfer chamber. To pass a semiconductor wafer between chambers elongated apertures or "slits" are provided in the walls between the chambers. These apertures can be selectively opened or closed by means of slit valves.
There are a great many types of slit valves known in the prior art. For example, in U.S. Pat. No. 4,785,962 of Toshima a vacuum chamber slit valve is disclosed which includes a door pivotally mounted near an aperture and pneumatically actuated cam follower rollers which selectively pivot the door between an open and closed position. Another approach is taken by Hutchinson in U.S. Pat. No. 4,715,764 who teaches a gate valve having an angularly disposed seat portion and a mating angular closure portion which moves vertically towards the seat portion. A third approach is disclosed in Vacuum Valves 90, May 1, 1989, pp. 24-29, a product catalog of VAT, Inc. VAT, Inc. provides a rectangular valve having a stepped seat which is engaged by a mating gate which moves perpendicularly with respect to the aperture.
There are several problems with gate valves of the prior art. Firstly, they all include bearing surfaces within the chamber which can generate particulates by surface-to-surface friction. Secondly, the force required to hold the gate valves in their closed position tends to be relatively large because the closing force is always at an angle to the seat surface. In consequence, considerable force must be applied to the doors of prior art slit valves to properly seal them against their valve seats.